When an electric vehicle (EV) mode is switched to a hybrid electric vehicle (HEV) mode in a conventional eco-friendly vehicle, in order to match a time point at which a speed of an engine is synchronized with a speed of the motor to a time point at which an engine clutch engagement is available, the engine is operated before the time point at which the engine clutch engagement is available depending on a rising slope of a motor speed, i.e., a motor acceleration, by taking into account an engine operation time and a speed synchronization time of the engine and the motor.
However, the engine operation time and the speed synchronization completion time point vary depending on the vehicle and a vehicle state, and thus, it is difficult to precisely match the speed synchronization completion time point to the engine clutch engagement available time point.
In a case that the speed of the engine is synchronized with the speed of the motor before the engine clutch engagement available time point, an idling time of the engine increases.
In addition, in a case that the speed of the engine is synchronized with the speed of the motor after the engine clutch engagement available time point, the EV drive time increases.